the company bye energy is converting cessna 172s to electric power. the cessna 172 has an empty weight of 1,470 pounds (668 kg), an l/d of 15, and a useful load of 830 pounds (377 kg). the aircraft is equipped with 220 kg of lipo batteries that have a charge density of 180 watt hour/kg. assuming a propulsive efficiency of 0.8, what is the range for a maximum gross weight takeoff?